Linking the water bodies to reports is a great idea. I could set up a thread in the reports sections for each water body and consolidate all reports for that body of water into that thread. This thread would then be linked to the map. If a user clicked on that link, he would be taken to the corresponding thread in the reports section. Obviously, if the user does not have access to the reports, they would not be able to see the thread. That would be handled automatically by forum permissions.
As for the filters you mentioned, that's a little trickier because that would potentially reveal too much info for those with no reports section access. For example, if user filtered bass-->markham, the ponds with bass would show without the user having to participate in the project. That would essentially defeat the purpose of the pond project